64 BULLETIN OF THE BUSSEY INSTITUTION. 
In another trial, one gram of the pure dextrose was dissolved 
in a small quantity of water and 5 cc. of a normal solution of 
potash were added. The volume of this mixed solution was about 
12 cc. One half of it was heated on a water-bath for an hour 
and a half to 70° C., and the other half was heated on a boiling 
water-bath for the same length of time. Both the liquors took on 
a deep red color and that on the boiling bath had the odor of 
burnt sugar. Both the liquors were nearly but not quite neutral- 
ized with hydrochloric acid of 5 percent., and each of them was 
mixed with 25 drops of the phenylhydrazin acetate reagent. No 
indications of mannose-hydrazone were obtained in either case 
from these unevaporated lquids, probably because the solutions 
were too dilute to permit mannose-hydrazone to separate out. It 
will be noticed that in one of the experiments above recorded, 
which closely resembled this one, no indications of mannose were 
got when the unevaporated solution was tested, though good balls 
and crystals of mannose-hydrazone were obtained when the evap- 
orated solution was examined. 
Of course, the conditions that obtained in this series of experi- 
ments, where pure dextrose was brought into contact with weak 
alkaline solutions, differed considerably from those of actual prac- 
tice where the dextrose in the products of the hydrolyses was 
commingled with organic matters of various and unknown char- 
acters. It is conceivable perhaps that Some of these extraneous 
substances might act to shield dextrose from the influence of the 
alkali, but the experiments go to show clearly enough that in 
testing for mannose extreme care must be exercised to avoid the 
action of alkalies in all cases where dextrose is known to be 
present. 
No Mannose was detected in Maple Sugar. 
The presence of mannan in the wood of sugar maple trees, as 
set forth on pages 82-84 of Vol. III of the Bulletin of the Bussey 
Institution, suggested the inquiry whether the sugar prepared 
from the sap of such trees in the spring might not contain some 
mannose. ‘The following experiments made to test this question 
gave only negative results, though for the sake of completeness 
it might perhaps be well to make yet another trial, and to test the 
actual sap as obtained directly from the trees. 
